Circuit for providing electronic enrichment fuel compensation in an electronic fuel control system

ABSTRACT

A circuit for recognizing and providing full-load enrichment fuel compensation for an electronic fuel control system is described herein. The circuit is adapted to recognize a signal which may be an engine operating parameter indicative of engine operation under full load and to thereafter incrementally increase the duration of the fuel injection command pulse generated by the main electronic fuel control system. In those electronic fuel control systems which provide a fuel injection command pulse whenever a generated voltage waveshape is below a threshold value, the present invention contemplates altering the shape of the generated waveshape to delay its excursion through the threshold value.

United States Patent 1191 Reddy I Nov. 18, 1975 [75] Inventor: Junuthula N. Reddy, Horseheads,

[73] Assignee: The Bendix Corporation, Southfield,

Mich.

221 Filed: Jan. 20, 1972 21 App1.No.:219,275

Related U.S. Application Data [63] Continuation-in-part of Ser, No. 101,896, Dec, 28.

1970, Pat. NO. 3,734,068.

3,685,526 8/1972 Hobo 123/32 EA 3,742,919 7/1973 Suda 123/32 EA 3,763,833 1Q/1973 Rachel 123/32 EA 3,786,789 1/1974 Barr 123/32 EA Primary E.\-aminerChar1es J. Myhrc Assistant Eraminer-Ronald B. Cox Attorney, Agent, or FirmGera1d K. Flagg ABSTRACT A circuit for recognizing and providing full-load enrichment fuel compensation for an electronic fuel control system is described herein. The circuit is adapted to recognize a signal which may be an engine operating parameter indicative of engine operation under full load and to thereafter incrementally increase the duration of the fuel injection command pulse generated by the main electronic fuel control system. In those electronic fuel control systems which provide a fuel injection command pulse whenever a generated voltage waveshape is below a threshold value, the present invention contemplates altering the shape of the generated waveshape to delay its excursion through the threshold value.

16 Claims, 7 Drawing Figures [52] U.S. Cl. 123/32 EA; 123/32 EA [51] Int. Cl. F02B 3/00 [58] Field of Search 123/32 AB, 32 EA [56] References Cited UNITED STATES PATENTS 2,859,738 11/1958 Campbell 123/32 EA 3,464,396 9/1969 Scholl. 1.23/32 EA 3,593,692 7/1971 Scholl 123/32 EA 3,623,461 11/1971 Rabus 123/32 EA WAVE SHAPE GENERATOR VARIABLE REFERENCE LEVEL GENERATOR US. Patent N0v.18, 1975 Sheet10f3 3,919,981

FIGURE 5 TEMPERATURE I SENSOR BATTERY ELECTRONICwIO CONTROL UNIT TIMING PICKUP FIGURE U.S. Patent Nov. 18,1975 Sheet2Of3 3,919,981

I a l 46 56 as sIGNALs M 3 FROM TO INJECTOR TIMING vALuE MEANS PICKUP l6 4 0 SWITCHING 48 DEVICE FIGURE 2 so 42 I wAVE sHAPE GENERATOR VARIABLE FULL LOAD 52 REFERENCE ENRICHMENT LEVEL CIRCUIT GENERATOR r l 68 l 40 I VARIABLE wAVE SHAPE FIGURE 4 REFERENCE LEVEL GENERATOR GENERATOR C D PULSE WIDTH INCREASE I=OR FULL LOAD ENRICHMENT FIGURE 7 U.S. Patent Nov. 18,1975 Sheet30f3 3,919,981

FIGURE 6 CIRCUIT FOR, PROVIDING ELECTRONIC ENRICIIMENT FUEL COMPENSATION IN AN ELECTRONIC FUEL CONTROL SYSTEM CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of my then copending commonly assigned and hereinbelow specifically referenced US. application Ser. No. 101,896 filed Dec. 28, 1970 issued on May 23, 1973 as US. Pat. No. 3,734,068. This application is also related to my copending commonly assigned US. Patent Application Ser. Nos.

1. Ser. No. 219,490 filed Jan. 20, 1972 and issued on Nov. 13, 1973 as US. Pat. No. 3,771,502;

2. Ser. No. 226,486 filed Feb. 15, 1972;

3. Ser. No. 226,498 filed Feb. 15, 1972;

4. Ser. No. 445,411 filed Feb. 25, 1974 5. Ser. No. 471,511 filed May 20, 1974 as a reissue of US. Pat. No. 3,771,502.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is related to the field of electronic fuel control systems for internal combustion engines and particularly to that portion of the abovedescribed field which is concerned with the provision of accurately metered quantities of fuel during transient operating conditions of an internal combustion engine. In particular, the present invention is concerned with that portion of the above-noted field which provides increased quantities of fuel for consumption by the engine when it is operating under a full-load con dition.

2. Description of the Prior Art Full load" as used herein means that condition of engine operation which produces a manifold pressure which is substantially within percent of the ambient atmospheric pressure. The prior art teaches that a condition of full load may be determined by mechanically or electrically sensing the position of the air-controlling throttle plate and, when such a full load indicative position is sensed, to provide an increase in the quantities of fuel delivered to the engine. However, such an im plementation involves several areas of inaccuracy and difficulty. Firstly, mechanical sensing or mechanically positioned electrical contacts are subject to positioning errors and need frequent recalibration in order to insure accuracy. Secondly, such implementations in a simple and economically convenient form permit only a digital determination that the full load enrichment requirement is in force. The thereafter provided increments of fuel for full load enrichment purposes will be substantially uniform and will not thereafter conform to the actual engine requirements. Furthermore, systems which rely upon mechanical devices for the sig nalling purpose are subject to relatively short life when compared with the automotive manufacturerss desire of 50 to 100,000 mile life capability of their vehicle and engine systems. It is therefore an object of the present invention to provide a means for providing full load en richment quantities of fuel which does not rely upon mechanical contacts to signal the need for full load enrichment. It is a still further object of the present invention to provide a circuit which is capable of recognizing varying degrees of the full load enrichment requirement to provide enrichment quantities of fuel which may vary in accordance with need. It is a still further object of the present invention to provide in a purely electronic circuit form a means for recognizing and providing full load enrichment quantities of fuel and which is capable of meeting the automotive manufacturers goal of 50 to 100,000 miles life capability.

' SUMMARY OF THE PRESENT INVENTION The present invention provides a circuit for recognizing whether or not the engine is operating in a condition which would require full load enrichment and to thereafter vary the fuel supply controlling pulses to lengthenthose pulses in accordance with the degree to which engine operation has been extended into the re gion of the full load enrichment requirement. The present invention makes use of the fact that the full load enrichment requirement may be identified by engine manifold pressures in excess of a predetermined value which may be, for example, atmospheric pressure minus torr. One form of the present invention therefore receives, as an input signal, a signal indicative of the instantaneous engine manifold pressure and a refer ence signal for comparison purposes. When the circuit recognizes that the manifold pressure has increased beyond the reference value, a switching circuit is activated to energize a current sink to decrease a value of a current which is then charging a timing capacitor. In this fashion, the rate of increase in the voltage across the timing capacitor will be reduced. In this manner, engine operation which is just slightly into the full load enrichment requirement region will receive just a small quantity of additional fuel for enrichment purposes while an engine which is opeating well into the region here full load enrichment quantities of fuel are required will receive a greatly enlarged quantity of fuel.

In a preferred form of the present invention, the generated waveshape is provided with a full load enrichment portion and-variations of the threshold level in response to manifold pressures indicative of full load are arranged to be at values in excess of the minimum value of the full load enrichment portion. As the present invention contemplates a fully electronic circuit which makes use of electronic signals present within an operating electronic fuel control system, the life objectives of the present invention are readily achieved.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows, in diagrammatic form, an electronic fuel control system for an internal combustion engine with which the present invention is of utility.

FIG. 2 shows a block diagram of one form of electronic control unit for use in the system of FIG. 1.

FIG. 3 shows an expanded block diagram of one portion of the FIG. 2 block diagram illustrating one form of the present invention.

FIG. 4 shows an expanded block diagram of one portion of the FIG. 2 block diagram illustrating an alternative form of the present invention.

FIG. 5 shows an electronic circuit realization of the present invention for use in the FIGS. 3 and 4 block diagrams.

FIG. 6 shows an electronic circuit realization according to FIGS. 2, 3, and 4 with which the present invention is of utility.

FIG. 7 shows a voltage composite waveform, a triggering pulse and a pulse length graph to illustrate the advantages of the present invention.

DETAILED DESCRIPTION OF THE DRAWING Referring now to FIG. 1, an electronic fuel control system is shown in schematic form. The system is comprised of a main computing means or electronic control unit 10, a manifold pressure sensor 12, a temperature sensor 14, an input timing means 16 and various other sensors denoted as 18. The manifold pressure sensor 12 and the associated other sensors 18 are illustrated mounted on throttle body 20 but it will be understood that other mounting locations are possible. The output of the computing means is coupled to an electromagnetic injector valve member 22 mounted in intake manifold 24 and arranged to provide fuel from tank 26 via pumping means 28 and suitable fuel conduits 30 for delivery to a combustion cylinder 32 of but one of several forms of an internal combustion engine otherwise not shown. While the injector valve member 22 is illustrated as delivering a spray of fuel toward an open intake valve 34, it will be understood that this representation is merely illustrative and that other delivery arrangements are known and utilized. Furthermore, it is well known in the art of electronic fuel control systems that computing means 10 may control an injector valve means comprised of one or more injector valve members 22 arranged to be actuated singly or in groups of varying numbers in a sequential fashion as well as simultaneously. The computing means is shown as energized by battery 36 which could be a vehicle battery and/or battery charging system as well as a separate battery.

The block diagramshown in FIG. 2 illustrates the computing means 10 of FIG. 1 in a nonparticularized manner as applied to a fuel system utilizing two-group injection. In FIG. 2, there is shown a switching device 38 capable of producing alternating output signals and receiving as input a signal or signals representative of engine crank angle as from sensor 16 of FIG. 1. Me chanically, sensor 16 could be a single-lobed cam, driven by the engine and alternately opening and closing a pair of contacts. Since this arrangement could generate spurious signals, as by contact bounce, the switching device 38 will be described and discussed as a flip-flop since the flip-flop is known to produce a substantially constant level of output at one output location and zero level at theother output location in response to a triggering signal which need only be a spike input as illustrated by traces 1 and 2 but may also be of longer duration and a flip-flop may be readily made insensitive to other types of signals. Signals received on the nontriggering input will, of course, have no effect .on a flip-flop. Outputs 40 and 42 are connected to the input of unit 50 and are also connected to the inputs of a pair of AND gates with output 40 being connected to one input of AND gate 46 and the output 42 being connected to one input of AND gate 48. Unit 50 is illustrated as receiving as its control input a signal from the pressure sensor 12 indicative of an engine operating condition and, therefore, of the engine fuel requirement. Sensor 12 is here shown coupled to a manifold lead or runner 52. The actual location of sensor 12 will depend upon the dynamic characteristics of the intake manifold and throttle body. Unit 50 also receives signals from temperature sensor 14 and it will be understood that use of the other sensor inputs though not illustrated is contemplated. However, for the sake of simplification, the additional control inputs have not been shown. The output of the unit 50 is connected to a second input of each AND gate 46 and 48. The output of AND gate 46 is connected to amplifier 56 which, in turn, supplies controlling current to the first injector group. AND gate 48 is connected to amplifier 58 which supplies controlling current to the second injector group. i

As will be readily apparent, the presence of an output signal from the flip-flop 38 will occur at one output location to the exclusion of the other. This signal will then appear at one input of only one AND gate of only one amplifier. This signal selectively designates an injector or injector group for imminent injection. For the sake of example, we shall assume that the output signal of the flip-flop 38 is at output location 40 so that the signal also appears at one input of AND gate 46. The signal from the output 40 of the flip-flop 38 also appears at the gate 44 where, assuming the flip-flop 38 has just changed state, a short duration signal is passed to the unit 50. Unit 50 is operative to produce an output during the passage of a predeterminable amount of time. This time is determined by the values of the sensory inputs applied to unit 50. During this initial period of time the output of the unit 50 is providing a fullstrength output signal. This signal is applied to one input of each of the AND gates 46 and 48. Because of the intrinsic nature of AND gates, an output signal is produced only while an input signal is being applied to each and every input. This then dictates that AND gate 46 will produce an output to be amplified by amplifier 56 to open the first injector group since it is receiving an injector selection command directly from the flipflop 38 and an injector control command from the unit 50. At the end of the time delay period, unit 50 produces a zero level signal so that the injection control command output signal is removed from the input to the AND gate 46 and the output of the AND gate 46 goes to zero, thereby allowing the first injector group to close. During the period of time the first injector group is open, a metered amount of fuel under pressure is injected by the first injector group. Depending upon particular electronics selected, suitable amplifiers and- /or inverters maybe used to match obtainable signals with desired or necessary circuit responses.

Referring now to FIG. 3, the unit 50 of FIG. 2 is illustrated as a plurality of functional blocks. The unit 50 is comprised of a waveshape generator 60, a variable reference level means 62, and the full load enrichment means 64 of the present invention. The waveshape generator 60 receives the triggering information from flip flop 38 and generates a voltage waveshape in response thereto such as is illustrated by waveshape in FIG. 7. The electronic circuit diagram of FIG. 6 shows one way of generating the desired waveshape and will be discussed in greater detail hereinbelow. Additionally, applicants co-pending commonly assigned application Ser. No. 101,896, filed Dec. 28, 1970, now issued as United States patent 3,734,068 and titled Fuel Injection Control System provides further discussion and illustration of electronic circuits to achieve the waveshape generating function of generator 60. The waveshape voltage is applied to variable reference level means 62 and full load enrichment means 64 through parallel circuit paths. The variable reference level means 62 receives a signal from the pressure sensor 12 to establish a switching level. An electronic realization of this unit is also illustrated in FIG. 6. It should be noted that the pressure signal input received by the variable reference level means 62 may be communi cated directly of sensor 12 or it may be suitably processed to provide a desired relationship between pressure variations and threshold variations. Such processing as may be desired is taught in my copending commonly assigned applications Ser. No. 170,566, filed Aug. 10, 1971 and titled Pressure Signal Shaping Network and Ser. No. 170,564 filed Aug. 10, 1971 and titled Method and Apparatus for Providing A Nonlinear Pressure Transducer Output Signal. The full load enrichment means 64 receives a variable signal at input port 66 which corresponds to outlet port 66 of FIG. 6 and which, in this instance, is the generated waveshape and compares the waveshaoe against a reference value. The reference value may be selected or determined through analytical or empirical testing for particular engine design configurations. The full load enrichment means 64 may be arranged to provide an output signal as at 68 which is indicative of whether or not the generated waveshape voltage is greater than or less than the established reference denoted here as R. By suitable circuit configurations such as illustrated in FIG. 5, the full load enrichment means 64, or for that matter, the waveshape generator means 60 may be arranged to alter the waveshape when it passes through the reference level. This altered waveshape would then be applied to the threshold establishing means in order to accomplish the full load enrichment pulse lengthening objectives of the present invention.

Referring now to FIG. 4, an alternate arrangement of signal processing to that illustrated in FIG. 3 is shown. Since substantially the same units are illustrated in FIG. 4 as were illustrated in, and discussed with reference to, FIG. 3 the same identifying numerals have been applied to the corresponding units. FIG. 4 differs from FIG. 3 primarily in the sequence of information processing. Full load enrichment means 64 receives, as its variable input 66, the pressure signal generated by sensor 12. This could be the same signal as received by variable reference level means 62 (i.e., either as generated or as processed) or it may receive different processing to provide a different pressure response characteristic than that provided to variable reference level means 62. As with the FIG. 3 embodiment, the variable signal 66 is compared with a reference signal R to generate an output signal at 68 for affecting the operation of waveshape generating means 60 in the manner described hereinabove.

Referring now to FIG. 5, an electronic circuit realization of full load enrichment means 64 is illustrated. The

enrichment means 64 includes a bistable comparison.

circuit 70 having a pair of transistors 72, 74, a switching means in the form of transistor 76 and a circuit means 78 actuable in response to the switching means 76 operative to controllably vary the waveshape generated by the generator means 60 of FIGS. 3 and 4. The circuit means 78 is here illustrated as a current sink having a control transistor 80 and a current dissipating resistor 82.

The R reference signal is generated by a voltage divider network comprised of resistors 84, 86 interconnecting the source of voltage B+ with the common or ground. The voltage source B+ may be, for instance, the vehicle battery 36 or the commonly provided battery charging system or it may be a separately provided voltage source. The junction of resistors 84, 86 is cou pled to the base or control electrode of transistor 74 and this connection is identified as R to correspond with the similarly designated signal input of FIGS. 3 and 4. This reference signal may be ofa fixed value but it is preferable to provide for variations in the ambient pressure by provided compensation in the form of the known ambient pressure compensation techniques. For example one of resistances 84, 86 may include a pressure responsive potentiometer portion responsive to the ambient pressure. The collector of transistor 74 is connected to the voltage source, B+, and the emitter of transistor 74 is coupled to the emitter of transistor 72. Both emitters are connected to resistor 88 going to ground. The base of transistor 72 is adapted to receive the variable input signal from input 66. The arrangement is commonly known as an emiter-coupled pair and is adapted to have one, and only one, of the transistors 72, 74 in conduction at anyone time. The transis tor in conduction in the arrangement illustrated which utilizes npn transistors will be the transistor whose base or control electrode receives the more positive voltage signal. When the transistor 72 goes into conduction, the current flow through the collector electrode will cause a current flow through the emitter-base junction of transistor 76 of the switching means and circuit means 78 will be switched into an on or active mode.

Referring now to FIG. 6, an electronic circuit is illustrated to satisfy the function requirements of blocks 60 and 62 in the block diagrams of FIGS. 3 and 4. The waveshape generating circuit means 60 is comprised of a pair of current sources 601, 602 which are alternately applied to a pair of capacitors 603, 604 by a switching network 605 receiving the triggering signals 40, 42. The rate at which the capacitors 603, 604 are initially charged and are discharged is controlled by network 606 also receiving the triggering signals 40, 42. Variable reference level means 62 samples the highest voltages appearing across capacitors 603, 604 and compares this value with the level established by the pressure sensor means signal as described hereinabove.

The current source 601 is comprised of transistor 101 whose base is connected to the junction of a pair of voltage dividing resistors 110, 111 and whose emitter is connected to resistor 112. The resistors 111 and 112 are connected to a source of potential identified as B+ and resistor goes to ground. Current source 602 is similarly comprised of a transistor 102 whose base is coupled to the junction of voltage divider resistors 114, 115 and whose emitter is connected to resistor 113 which is also connected to the B+ source. This arrangement is operative to establish a known level of constant current flow in the collectors of transistors 101, 102, respectively. The collector of transistor 101 is then connected in a parallel fashion to the collectors ofa pair of transistors 131, 132. Similarly, the collector of transistor 102 is connected in parallel to the collectors of a pair of transistors 133, 134. The base of transistors 131 and 134 are connected together through resistances 141, 142 while the bases of transistors 132, 133 are connected by way of resistances 143, 144. The junction of resistances 141, 142 is arranged to receive the trigger signals as at 40 while the junction of reistances 143, 144 is arranged to receive the trigger signals as at 42. The emitters of transistors 13] and 133 are connected to capacitor 603 while the emitters of transistors 132 and 134 are connected to capacitor 604. This circuit is then arranged to provide the current flow from current source 601 through transistor 131 to capacitor 603 and the current from source 602 through transistor 134 to capacitor 604whenever a high voltage signal is present on lead 40 and a low voltage signal is present on lead 42. Whenever a low voltage signal is present on lead 40 and a high voltage signal is present on lead 42, the current from source 601 will flow through transistor 132 to capacitor 604, while the current from source 602 flows through transistor 133 to capacitor 603. The full load enrichment means 64 are operative to provide a current sink to selectively extract current from the network feeding current into the capacitors 603, 604. In this fasion, the instantaneous voltage across the capacitors 603, 604 can be controlled in a preprogrammed fashion so as to influence the voltage appearing at circuit lead 66. By means of the diodes 161, 162 which are directly connected to the capacitors 603, 604 the voltage appearing atcircuit lead 66 will be a value representative of the highest of the voltage drops across capacitors 603, 604.

Network 606 is comprised of first, second, third and fourth control transistors, numbers 135, 136, 137, and 138, respectively, a plurality of voltage level establishing resistor pairs 139, 140, and a plurality of voltage level establihing diode means 145 through 150. Reset means 151, and additional voltage level establishing diodes 152, 153, are also illustrated. Change of state of the flip-flop 38, as illustrated in FIG. 2, will reverse the high-low signal relationship appearing on triggering leads 40, 42, and the appearance ofa high signal on one gate, for instance lead 40, will result in the generation of a reset pulse from reset means 151 which can be arranged to be a relatively high level signal. For example, reset means 151 may be a monostable multivibrator or other circuit arranged to generate a high level signal for a predtermined period of time upon the receipt of a high level triggering signal. The presence of these high level signals at circuit lead 40 and at the output of reset means 151 will cause junction 154 to be at a relatively high level and, through diode means 147, transistor 138 will be conduction. This will, in turn, cause transistor 137, having its emitter connected to capacitor 603, to be in conduction so that the voltage then appearing across capacitor 603 will be dumped as a current flow to ground through the conducting transistors 137, 138. This voltage dump will continue until the voltage appearing across capacitor 603 reaches a low level determined by the number of pn junctions between capacitor 603 and ground. During this time interval, current flow from current source 101 through transistor 131 will be dumped to the extent that it would represent ex cess voltage across capacitor 603. Upon the termina tion of the reset pulse from reset means 151, the voltage at junction 54 will drop and. due to the plurality of diodes in diode means 147, will be insufficient to maintain transistor 138 in conduction. This will cause transistor 138 and in turn transistor 137 to switch of, thereby terminating the voltage dump of capacitor 603 and also permitting the current flow from current source 601 to increase the voltage level across capacitor 603. With reference to FIG. 7, the time interval of the reset pulse 151 would correspond to the initial charging interval AB on curve 90, while the time interval B-C would represent the period during which capacitor 603 is being charged by the current source 101. The level indicated by the C-D line of curve 90 of FIG. 7 represents a level when the charge across capacitor 603 is sufficiently high relative to the voltage level established by the voltage divider effects of resistors 110, l l 1, that the base-collector junction of transistor 101 is forward biased, and the transistor is in saturation. The operation of network 606 with regard to the receipt of a high level signal on triggering lead 42 is substantially the same as described hereinabove in view of the fact that the network 606 is comprised of two substantially identical havles, one of which has been described in detail herein. By suitable selecting the resistive values along with maintaining a relatively small capacitor value of capacitor 603, it'can be arranged that the discharge of capacitor 603 down to the level represented by the AB portion of curve in FIG. 7 can occur in a very brief time scale relative to the duration of a triggering pulse.

Variable reference level means 62 receives a signal indicative of the manifold pressure at 170 and this sig nal is applied to the base of transistor 172. The base of transistor 171 receives the signal from circuit lead 66. As the emitters of transistors 171, 172 are coupled together, one of these transistors will be in conduction depending upon which has a base residing at a higher voltage value. When the value appearing on circuit lead 66 exceeds the value appearing on circuit input 170, transistor 171 will go into conduction and transistor 172 will drop out of conduction. Termination of conduction of transistor 172 will consequently terminate conduction of transistor 173. While transistor 172 was conducting, transistor 173 was also conducting and a relatively high voltage signal was present at circuit location 174 due to the voltage divider action of resistors 182-, 183. However, termination of conduction of transistor 173 will result in a substantially zero or ground level signal appearing at circuit location 174 due to the lack of current flow through the resistors 182, 183. This output signal may be applied to the AND gates 46, 48 in the FIG. 2 embodiment to constitute an injection command signal.

Referring now to FIGS. 5, 6, and 7, the operation of the present invention will be illustrated. A series of triggering pulses will be received on circuit leads 40, 42, such that they are complimentary. That is, the presence of a pulse on circuit lead 40 indicates the absence of a pulse on circuit lead 42 and the presence of a circuit pulse on circuit lead 42 represents the absence of a cir cuit pulse on circuit lead 40. Receipt of a circuit pulse on circuit lead 40 will cause current I to be applied to capacitor 603 and current I to be applied to capacitor 604. Termination of the pulse on circuit lead 40 and the generation of the pulse on circuit lead 42 will cause capacitor 604 to be dumped through transistor and to be immediately charged with current I, while the current 1 is applied to capacitor 603 to generate a further charge thereon. Particularly with reference to FIG. 7, the curve identified as 90 will be generated with that portion between the letters A and D being generated by the flow of current I into a capacitor 603 or 604 and that portion having a magnitude greater than that at D, the computing portion, being generated by the flow of current 1 into the same capacitor. As can be seen, point D coincides in time with the occurrence, for purposes of this illustration, of trigger pulse 42. Circuit lead 66 is at a voltage value which is the largest of the voltages across capacitors 603, 604 and is communicated to the base of transistor 72 in the full load enrichment circuit 64 and as soon as its voltage value exceeds the reference valueuthe current sink 78 will go into operation and will extract current from circuit lead 68 which is communicated to the 1 current source. This will result in lessening the slope of the curve 90. As can be seen from FIG. 7, if the reference value is as represented by the R point and the threshold level is represented by 92, the decrease in slope of curve 90 will result in a lengthening of pulse 94 with the actual amount of the lengthening being dependent upon the magnitude of the difference between the threshold level 92 and the R breakpoint, or in other words the degree to which engine operation has extended into the full load enrichment requirement.

It should be noted that the FIG. 5 embodiment is intended to be merely illustrative and that modifications may be made therein, for example, the circuit means 78 could also be a current source which adds current to that provided by current source 602. The switching means 76 could then be arranged to terminate the communication of this additional current to the appropriate capacitor to achieve the desired slope reduction and concomitant pulse lengthening.

I claim:

1. In an internal combustion engine fuel control sys' tem of the type having an intake manifold for providing air to the engine, sensor means including means for generating a signal indicative of engine load, and computing means responsive to the sensor means for providing a train of fuel delivery command signals varying from an engine speed determined first value to a sec ond value determined at least in part by said signal indicating engine load, the durations of said fuel delivery command signals between said engine speed determined first value and said second valve determining quantities of fuel supplied to the engine, the improvement comprising a full load enrichment circuit having:

means for providing a reference signal representing a predetermined engine load at which the air pressure in the intake manifold is within ten percent of atmospheric pressure; and

means for comparing the reference and load indicating signals and changing the duration of the fuel delivery command signals in response to load indicating signal values having a predetermined relationship with respect to said reference signal.

2. The fuel control system of claim 1 in which:

said means for changing the duration of said fuel delivery command signals comprise:

current sink means; and

switching means responsive to the reference and engine load indicating signals for switchingly connecting said current sink means to drain energy from the means for providing said fuel delivery command signals and thereby increase the time required for a command signal to reach said second value.

3. The fuel control system of claim 2 in which:

the means for providing said train of fuel delivery command signals comprise a capacitor, and means for intermittently charging and discharging said capacitor; and

said switching means comprise means for connecting said current sink means to drain energy from said capacitor in response to an engine load indicating signal having a value greater than the value of said reference signal.

4. In an internal combustion engine fuel control system of the type having sensor means including means for generating a signal indicative of engine load, and computing means responsive to the sensor means for producing a train of fuel delivery command signals that vary from an engine speed determined first value to a second value, said signal indicating engine load determining said second value and thereby determining at least in part the time requiredfor a fuel delivery command signal to reach said second value. the durations of said fuel delivery command signals between said engine speed determined first value and said second value determining the quantity of fuel supplied to the engine. the improvement comprising a full load enrichment circuit having:

means for providing a reference signal representing a predetermined engine load; and

means for comparing the reference and fuel delivery command signals and reducing the variation rate of each fuel delivery command signal reaching said reference value to thereby increase the quantity of fuel being supplied to the engine.

5. The fuel control system of claim 4 in which:

The means for providing said train of fuel delivery command signals comprise a capacitor and current source means for intermittently charging and discharging said capacitor; and i said means for reducing the variation of said fuel delivery command signals comprise:

current sink means for draining energy from said capacitor; and

switching means responsive to the reference and fuel delivery command signals for switchingly connecting said current sink means to said capacitor in response to a fuel delivery command signal reaching said reference value.

6. In an internal combustion engine fuel control sys tem of the type having sensor means, including means to generate a signal indicative of engine load, responsive to engine conditions operative to produce signals indicative of engine operating parameters, computing means responsive to the sensor means signals operative to produce a fuel delivery command signal indicative of the engine fuel requirement and fuel supply means responsive to the fuel delivery command signal operative to supply the engine with fuel in relation to the fuel delivery command signal, wherein the computing means comprise waveform generating means operative to generate a composite waveform signal having an initializing portion defining an engine speed determined initializing level and a computing portion having a predetermined slope increasing from said initializing level and threshold means receiving said waveform on one of said sensor signals operative to establish a sensor signal determined threshold level, and further operative to generate an output signal whenever the computing portion of the waveform signal has a level which has a selected relationship with the established threshold, the improvement comprising electronic circuit means responsive to the sensor means signal indicativeof a condition of engine loading in excess of a predetermined amount operative to generate a signal indicative of a need for full load enrichment, wherein said electronic circuit means comprise switching means having a pair of stable states responsive to the computing portion of the waveform signal having attained a preselected value operative to switch from one state to the other to generate a signal indicative of the instantaneous relationship between the computing portion and said preselected value, and

means responsive to said enrichment signal operative to modify the fuel delivery command signal to cause the fuel supply means to increase the delivery of fuel to the engine, said enrichment signal responsive means being responsive to said switching means indication of a predetermined relationship between the computing portion and the preselected value and are operative to alter the slope of the computing means signal.

7. The system as claimed in claim 6 wherein said waveform generating means comprise current source means operative to generate an electrical current and receiving means intermittently receiving said current source means current operative to generate a signal having a level indicative of the duration said current has been received and said enrichment signal responsive means comprise current sink means operative when actuated to reduce the level of current being received by said receiving means.

8. In an internal combustion engine fuel control system of the type having a plurality of sensor means responsive to engine conditions operative to generate signals indicative of engine operating parameters, computing means responsive to the sensor means signals operative to produce a fuel delivery command signal indicative of the engine fuel requirement and fuel supply means responsive to the fuel delivery command signal operative to supply the engine with fuel in relation to the fuel delivery command signal wherein the computing means comprises first generating means for generating a voltage signal waveform having predeterminable first and second waveform portions and second generating means for generating the fuel delivery command signal while the second waveform portion remains below a sensor means signal controlled second value, said first portion defining a first value varying with engine speeds and said second portion commencing at said first value and increasing towards said second value the improvement to said computing means comprising:

circuit means responsive to at least one of said plurality of sensor means operative to generate a signal indicative of engine operation within a selected range of engine conditions coupled to the computing means first generating means operative to controllably vary the slope of thesecond waveform portion in response to the degree of engine operation within said selected range.

9. The system as claimed in claim 8 wherein the first generating means comprise capacitor means, at least two current source means and switching means to sequentially apply the currents generated by the current source means to the capacitor means, the first current sourceoperative to generate the first waveform portion across the capacitor means and the second current source means operative to generate the second waveform portion across the capacitor means and said circuit means comprise means for generating a control signal in response to engine operation within a selected range of engine operating conditions and means for applying said control signal to the second current source means, said control signal operative to control the magnitude of the current generated by the second current source means.

10. The system as claimed in claim 9 wherein said control signal is operative to terminate the communication of current generated by said second current source means.

1 1. In an internal combustion engine fuel control system of the type having sensor means responsive to engine conditions operative to produce at least one signal indicative of engine operating parameters, computing means responsive to the sensor means signal operative to produce a fuel delivery command signal indicative of the engine fuel requirement and fuel supply means responsive to the fuel delivery command signal, the computing means including first means for generating a predeterminable waveshape signal and second means for generating a threshold level and responsive to the generated waveshape operative to produce as output signal the fuel delivery command signal while the generated waveshape bears a preselected relationship to the threshold level wherein the first generating means comprise capacitor means, at least two current source means and switching means to sequentially apply the current generated by the current source means to the capacitor means, the first current source operative to generate an engine speed determined first waveform portion across the capacitor means and the second current source means operative to generate a second waveform portion across the capacitor means increasing from said first portion the improvement comprising:

circuit means coupled to said first means and responsive to selected conditions of the generated waveshape operative to controllably alter the waveshape and said circuit means comprising means for generating a control signal in response to engine operation within a selected range of engine operating conditions and means for applying said control signal to the second current source means, said control signal operative to control the magnitude of the current generated by the second current source means.

12. The system as claimed in claim 11 wherein said control signal is operative to terminate the communication of current generated by said second current source means.

13. In an internal combustion engine fuel control system of the type having an intake manifold for providing fuel to the engine, sensor means including means for generating a load signal indicative of intake manifold air pressure, and computing means responsive to the sensor means for providing a train of fuel delivery command signals having durations determined at least in part by said signal indicating manifold air pressure, the durations of said fuel delivery command signals determining quantities of fuel supplied to the engine, the improvement comprising a full load enrichment circuit having:

means for providing a reference signal representing a predetermined relationship with respect to atmospheric pressure and for varying said reference signal in accordance with atmospheric pressure variation; and

means for comparing the reference and load indicating signals and changing the duration of the fuel delivery command signals in response to load indicating signal values having a predetermined relationship with respect to said reference signal.

14. In an internal combustion engine fuel control system of the type having an intake manifold for providing fuel to the engine, sensor means including means for generating a load signal indicative of intake manifold air pressure, and computing means responsive to the sensor means for producing a train of fuel delivery command signals that vary from an engine speed determined first value to a second value, said load signal indicating manifold air pressure determining said second value and thereby determining at least in part the time required for a fuel delivery command signal to reach said second value, the durations of said fuel delivery command signals between said first and second values determining the quantity of fuel supplied to the engine, the improvement comprising a full load enrichment circuit having:

means for providing a reference signal representing a predetermined relationship with respect to atmospheric pressure and for varying said reference signal in accordance with atmospheric pressure variation; and

means for comparing the reference and fuel delivery command signals and reducing the variation rate of each fuel delivery command signal reaching said reference value to thereby increase the quantity of fuel being supplied to the engine.

15. In an internal combustion engine fuel control system of the type having a plurality of sensor means each responsive to a different engine operating condition to generate a respective engine operating parameter signal, electronic fuel command signal computing means comprising:

a. capacitor means;

b. first and second current source means for generating respective currents;

c. switch means for alternately coupling said capacitor means to said first and second current sources whereby a first waveform is provided by said capacitor means while said first current source is coupled thereto and a second waveform having successive first and second slopes is generated by said capacitor means when said second current source is coupled thereto;

d. first and second reference means for providing respective first and second reference signals varying in accordance with respective first and second engine operating parameter signals; and

e. first and second comparator means each having a first input, a second input and an output. said first input coupled to said capacitor means, said second input coupled to a different one of said first and second reference means, said output of said first comparator means operative to provide a fuel injection command signal commencing when said capacitor means is switched from said first current source means to said second current source means and terminating when said second waveform exceeds said first reference signal, and said output of said second comparator means coupled to said second current source means to vary the current generated thereby from said first slope to said second slope said second waveform exceeds said second reference signal;

wherein said second waveform increases along said first slope as long as said second waveform is less than said second reference signal whereafter said second waveform increases along said second slope so that after said second waveform exceeds said second reference signal the time required to reach said first reference signal is changed from it would have been if said second comparator means had not varied the current generated by the second source means.

16. In the electronic fuel command computing circuit of claim '15 said switching means operative to effect selective discharge and charge of said capacitor means when coupled to one of said first and second current source means in accordance with the time elapsed from the switching of said capacitor means from said second current source means to said first current source means and said second comparator output operative to decrease the current generated by said second current source means to effect fuel enrichment when said first reference signal is greater than said second reference UNITED STATES PATENT UFFICE CERTIFICATE 0F cQRECTw Q PATENT NO. 3,919,981

DATED 3 November l8, 1975 |NVENTOR(S) Junuthula N. Reddy It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN DETAILED DESCRIPTION OF THE DRAWING Column 6, Line 62 change "reist-" to resist;

. Column 7, Line l3 change "fasion" to fashion--;

Column 7, Line 25 change "establihing" to establishing- Column 7, Line 36 change "predtermined" to predetermined- Column 7, Line 55 change "54" to l54--;

Column 7, Line 58 change "of" to off";

Column 8, Line 9 change "havles" to halves--; Column 8, Line l0 change "suitable" to suitably--; O

IN THE CLAIMS Claim l Column 9, Line 35 change "value" to valve--;

Claim 15, Column l4, Line 22 change "wherein" to whereby.

Signed and Scale tie twenty-second Day 0? June 1976 [SEAL] Arresr:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oflarenrs and Trademarks 

1. In an internal combustion engine fuel control system of the type having an intake manifold for providing air to the engine, sensor means including means for generating a signal indicative of engine load, and computing means responsive to the sensor means for providing a train of fuel delivery command signals varying from an engine speed determined first value to a second value determined at least in part by said signal indicating engine load, the durations of said fuel delivery command signals between said engine speed determined first value and said second valve determining quantities of fuel supplied to the engine, the improvement comprising a full load enrichment circuit having: means for providing a reference signal representing a predetermined engine load at which the air pressure in the intake manifold is within ten percent of atmospheric pressure; and means for compariNg the reference and load indicating signals and changing the duration of the fuel delivery command signals in response to load indicating signal values having a predetermined relationship with respect to said reference signal.
 2. The fuel control system of claim 1 in which: said means for changing the duration of said fuel delivery command signals comprise: current sink means; and switching means responsive to the reference and engine load indicating signals for switchingly connecting said current sink means to drain energy from the means for providing said fuel delivery command signals and thereby increase the time required for a command signal to reach said second value.
 3. The fuel control system of claim 2 in which: the means for providing said train of fuel delivery command signals comprise a capacitor, and means for intermittently charging and discharging said capacitor; and said switching means comprise means for connecting said current sink means to drain energy from said capacitor in response to an engine load indicating signal having a value greater than the value of said reference signal.
 4. In an internal combustion engine fuel control system of the type having sensor means including means for generating a signal indicative of engine load, and computing means responsive to the sensor means for producing a train of fuel delivery command signals that vary from an engine speed determined first value to a second value, said signal indicating engine load determining said second value and thereby determining at least in part the time required for a fuel delivery command signal to reach said second value, the durations of said fuel delivery command signals between said engine speed determined first value and said second value determining the quantity of fuel supplied to the engine, the improvement comprising a full load enrichment circuit having: means for providing a reference signal representing a predetermined engine load; and means for comparing the reference and fuel delivery command signals and reducing the variation rate of each fuel delivery command signal reaching said reference value to thereby increase the quantity of fuel being supplied to the engine.
 5. The fuel control system of claim 4 in which: The means for providing said train of fuel delivery command signals comprise a capacitor and current source means for intermittently charging and discharging said capacitor; and said means for reducing the variation of said fuel delivery command signals comprise: current sink means for draining energy from said capacitor; and switching means responsive to the reference and fuel delivery command signals for switchingly connecting said current sink means to said capacitor in response to a fuel delivery command signal reaching said reference value.
 6. In an internal combustion engine fuel control system of the type having sensor means, including means to generate a signal indicative of engine load, responsive to engine conditions operative to produce signals indicative of engine operating parameters, computing means responsive to the sensor means signals operative to produce a fuel delivery command signal indicative of the engine fuel requirement and fuel supply means responsive to the fuel delivery command signal operative to supply the engine with fuel in relation to the fuel delivery command signal, wherein the computing means comprise waveform generating means operative to generate a composite waveform signal having an initializing portion defining an engine speed determined initializing level and a computing portion having a predetermined slope increasing from said initializing level and threshold means receiving said waveform on one of said sensor signals operative to establish a sensor signal determined threshold level, and further operative to generate an output signal whenever the computing portion of the waveform signal has a level which has a selected relationship with the established threshold, the improvement comprising: electronic circuit means responsive to the sensor means signal indicative of a condition of engine loading in excess of a predetermined amount operative to generate a signal indicative of a need for full load enrichment, wherein said electronic circuit means comprise switching means having a pair of stable states responsive to the computing portion of the waveform signal having attained a preselected value operative to switch from one state to the other to generate a signal indicative of the instantaneous relationship between the computing portion and said preselected value, and means responsive to said enrichment signal operative to modify the fuel delivery command signal to cause the fuel supply means to increase the delivery of fuel to the engine, said enrichment signal responsive means being responsive to said switching means indication of a predetermined relationship between the computing portion and the preselected value and are operative to alter the slope of the computing means signal.
 7. The system as claimed in claim 6 wherein said waveform generating means comprise current source means operative to generate an electrical current and receiving means intermittently receiving said current source means current operative to generate a signal having a level indicative of the duration said current has been received and said enrichment signal responsive means comprise current sink means operative when actuated to reduce the level of current being received by said receiving means.
 8. In an internal combustion engine fuel control system of the type having a plurality of sensor means responsive to engine conditions operative to generate signals indicative of engine operating parameters, computing means responsive to the sensor means signals operative to produce a fuel delivery command signal indicative of the engine fuel requirement and fuel supply means responsive to the fuel delivery command signal operative to supply the engine with fuel in relation to the fuel delivery command signal wherein the computing means comprises first generating means for generating a voltage signal waveform having predeterminable first and second waveform portions and second generating means for generating the fuel delivery command signal while the second waveform portion remains below a sensor means signal controlled second value, said first portion defining a first value varying with engine speeds and said second portion commencing at said first value and increasing towards said second value the improvement to said computing means comprising: circuit means responsive to at least one of said plurality of sensor means operative to generate a signal indicative of engine operation within a selected range of engine conditions coupled to the computing means first generating means operative to controllably vary the slope of the second waveform portion in response to the degree of engine operation within said selected range.
 9. The system as claimed in claim 8 wherein the first generating means comprise capacitor means, at least two current source means and switching means to sequentially apply the currents generated by the current source means to the capacitor means, the first current source operative to generate the first waveform portion across the capacitor means and the second current source means operative to generate the second waveform portion across the capacitor means and said circuit means comprise means for generating a control signal in response to engine operation within a selected range of engine operating conditions and means for applying said control signal to the second current source means, said control signal operative to control the magnitude of the current generated by the second current source means.
 10. The system as claimed in claim 9 wherein said control signal is operative to terminate the communication of current generated by said second current source means.
 11. In an internal combustion engine fUel control system of the type having sensor means responsive to engine conditions operative to produce at least one signal indicative of engine operating parameters, computing means responsive to the sensor means signal operative to produce a fuel delivery command signal indicative of the engine fuel requirement and fuel supply means responsive to the fuel delivery command signal, the computing means including first means for generating a predeterminable waveshape signal and second means for generating a threshold level and responsive to the generated waveshape operative to produce as output signal the fuel delivery command signal while the generated waveshape bears a preselected relationship to the threshold level wherein the first generating means comprise capacitor means, at least two current source means and switching means to sequentially apply the current generated by the current source means to the capacitor means, the first current source operative to generate an engine speed determined first waveform portion across the capacitor means and the second current source means operative to generate a second waveform portion across the capacitor means increasing from said first portion the improvement comprising: circuit means coupled to said first means and responsive to selected conditions of the generated waveshape operative to controllably alter the waveshape and said circuit means comprising means for generating a control signal in response to engine operation within a selected range of engine operating conditions and means for applying said control signal to the second current source means, said control signal operative to control the magnitude of the current generated by the second current source means.
 12. The system as claimed in claim 11 wherein said control signal is operative to terminate the communication of current generated by said second current source means.
 13. In an internal combustion engine fuel control system of the type having an intake manifold for providing fuel to the engine, sensor means including means for generating a load signal indicative of intake manifold air pressure, and computing means responsive to the sensor means for providing a train of fuel delivery command signals having durations determined at least in part by said signal indicating manifold air pressure, the durations of said fuel delivery command signals determining quantities of fuel supplied to the engine, the improvement comprising a full load enrichment circuit having: means for providing a reference signal representing a predetermined relationship with respect to atmospheric pressure and for varying said reference signal in accordance with atmospheric pressure variation; and means for comparing the reference and load indicating signals and changing the duration of the fuel delivery command signals in response to load indicating signal values having a predetermined relationship with respect to said reference signal.
 14. In an internal combustion engine fuel control system of the type having an intake manifold for providing fuel to the engine, sensor means including means for generating a load signal indicative of intake manifold air pressure, and computing means responsive to the sensor means for producing a train of fuel delivery command signals that vary from an engine speed determined first value to a second value, said load signal indicating manifold air pressure determining said second value and thereby determining at least in part the time required for a fuel delivery command signal to reach said second value, the durations of said fuel delivery command signals between said first and second values determining the quantity of fuel supplied to the engine, the improvement comprising a full load enrichment circuit having: means for providing a reference signal representing a predetermined relationship with respect to atmospheric pressure and for varying said reference signal in accordance with atmospheric pressure variation; and means for comparing the reference and fuel delivery command signals and reducing the variation rate of each fuel delivery command signal reaching said reference value to thereby increase the quantity of fuel being supplied to the engine.
 15. In an internal combustion engine fuel control system of the type having a plurality of sensor means each responsive to a different engine operating condition to generate a respective engine operating parameter signal, electronic fuel command signal computing means comprising: a. capacitor means; b. first and second current source means for generating respective currents; c. switch means for alternately coupling said capacitor means to said first and second current sources whereby a first waveform is provided by said capacitor means while said first current source is coupled thereto and a second waveform having successive first and second slopes is generated by said capacitor means when said second current source is coupled thereto; d. first and second reference means for providing respective first and second reference signals varying in accordance with respective first and second engine operating parameter signals; and e. first and second comparator means each having a first input, a second input and an output, said first input coupled to said capacitor means, said second input coupled to a different one of said first and second reference means, said output of said first comparator means operative to provide a fuel injection command signal commencing when said capacitor means is switched from said first current source means to said second current source means and terminating when said second waveform exceeds said first reference signal, and said output of said second comparator means coupled to said second current source means to vary the current generated thereby from said first slope to said second slope said second waveform exceeds said second reference signal; wherein said second waveform increases along said first slope as long as said second waveform is less than said second reference signal whereafter said second waveform increases along said second slope so that after said second waveform exceeds said second reference signal the time required to reach said first reference signal is changed from it would have been if said second comparator means had not varied the current generated by the second source means.
 16. In the electronic fuel command computing circuit of claim 15 said switching means operative to effect selective discharge and charge of said capacitor means when coupled to one of said first and second current source means in accordance with the time elapsed from the switching of said capacitor means from said second current source means to said first current source means and said second comparator output operative to decrease the current generated by said second current source means to effect fuel enrichment when said first reference signal is greater than said second reference signal. 